The bishops say legalization will only add to the country's crisis with illicit drugs and prescription opioids. They point to peer-reviewed research that indicates marijuana is addictive and studies that show addicts started with alcohol and marijuana.

They dispute advocates' claims that legalization will eliminate the black market. They say it's possible the underground will simply sell it more cheaply and to minors.

Pritzker believes taxes on cannabis sales could produce up to $1 billion a year.